Multicast routing support for real-time applications.
Daniel Zappala · University of Southern California Digital Library · 2014
One approach to improving the performance of real-time applications over the Internet is to design new adaptive techniques, similar to the use of TCP for elastic applications. These techniques include adapting a receiver's audio playback point and varying a receiver's subscription to levels of hierarchically encoded video. Another approach is to upgrade the best-effort service model of the Internet to include enhanced levels of service characterized by reduced delay or increased bandwidth. Researchers in this area have proposed an integrated services architecture that uses a combination of scheduling algorithms, admission control, and a reservation protocol to control access to these service levels. While both of these approaches are promising, neither can be completely successful without a corresponding upgrade of the routing infrastructure. Real-time applications, whether they use adaptive techniques or integrated services, are currently limited to using shortest path, opportunistic routes. If an application is unable to obtain its desired service on the shortest path, routing does not supply it with an alternative route. Likewise, if an application is able to obtain its desired service on the current route, routing may opportunistically change to a new, shorter route, possibly resulting in a service disruption. This dissertation explores several interdomain multicast routing enhancements that can improve the performance of real-time applications. We propose extending multicast routing protocols to include alternate routes and pinned (non-opportunistic) routes. Routing may use these extensions on-demand in support of receivers that need them. We have designed a simple, scalable route setup protocol that re-configures multicast trees using an explicit route. We describe how this protocol prevents loops and compare it to several other alternatives. We have also developed a set of heuristics for constructing alternate paths and describe the results of a simulation study that evaluates these heuristics and demonstrates the validity of our approach. Beyond these fundamental extensions, we explore a broad set of additional services that routing protocols may use specifically to support RSVP, a reservation protocol that is part of the integrated services architecture. We present designs of these additional services and qualitatively analyze their mechanistic complexity.